# Angle between curve and sphere

1. Jul 21, 2011

### autre

I need to find the angle between a curve x^2 + y^2 =1, z = sqrt(2)x/y and a sphere z^2 + y^2 + z^2 = 1. I found two points of intersection, (0,1,0) and (0,-1,0), so at each of these points I assume that there's a tangent line to the curve and a tangent plane to the sphere. Then I'm guessing I'd find the angle between the direction vector of the tangent line to the curve and the normal vector of the tangent plane. Am I on the right track?

I have the direction vector of the tangent line to the curve at (0,1,0) as <1, 0, sqrt(2)> and at (0,-1,0) as <-1,0,-sqrt(2)>. I'm not sure where to go from here.

2. Jul 21, 2011

### micromass

Yes, that's good.

Well, find the tangent plane to the sphere at the points (0,1,0) and (0,-1,0).

3. Jul 21, 2011

### autre

Oh, so that'll just be a 90 degree angle in both cases, since <+-1, 0, +-sqrt(2)>.<0,+-2,0> = 0 so arccos0 = pi/2.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook